This invention relates generally to techniques for estimating the amount of release, or release rate, of a substance and, more particularly, to release of a toxic chemical. More particularly, the invention relates to estimating release of a toxic chemical in a liquid or gaseous state. The invention may be used to direct emergency response to an unfolding of the event, as well as to a post-event analysis or a pre-event preparation. The invention may be applied to fixed release locations, such as chemical facilities, as well as to portable events, such as may occur at a railroad car, a pipeline, or the like.
A significant challenge in any emergency scenario is the estimation of the amount of chemical being released. The impacted area to which the emergency responder is interested to know, in order to devise an escape route or evacuation zone or shelter in place, depends on the amount of chemical release, among other parameters. Therefore, having a good estimation of the release is very important.
An exemplary event may involve several derailed railroad cars leaking unknown amounts of chemical, or a plant process area engulfed in a toxic material with no way of observing where in the process the leak is occurring and how much chemical is being released. Each event is unique and may involve a very small amount of material, or be catastrophic in its scope. Initial estimates are very difficult and even an expert responder can only guess at the initial release. Therefore, a quick and accurate estimation of the release is crucial for the response agencies in warning the public and taking them out of harms way.
Existing release rate estimation schemes work best at fixed facilities that have solid process review programs and whose personnel clearly understand the highest probabilities for a release to occur. Events, of course, are not limited to fixed facilities, but can also be transportation-based, such as a railroad tank or car, barge, truck, or it can be in the form of a pipeline. With the wide range of chemical species that could be involved and the endless release possibilities, having techniques for quickly assessing the event is important. While known systems provide useful information about an event, they do not provide an assessment of the release for a significant portion of the duration of the event nor do they take into account the significance of changing meteorology.
The goal of the invention is to improve the accuracy of the amount of a chemical entering the ambient, and resulting impact area from the release, and to improve the speed of obtaining results in order to enhance response effort.
A method of estimating an amount of substance being released into an ambient, thereby creating a plume, includes making concentration measurements of the substance over a period of time and providing an estimate of the amount of the substance released as a function of the multiple concentration measurements and a time of the measurements. The method may further include considering atmospheric conditions of the ambient into which the substance was released. The considering of atmospheric conditions may include considering atmospheric conditions over the period of time. The considering of atmospheric conditions may include providing at least one weather sensor adapted to measure atmospheric conditions of the ambient into which the substance was released. The considering of atmospheric conditions may include downloading weather data from a global electronic network, downloading weather data from a government dial-up weather service, and/or estimating weather by a weather professional.
The estimate of the amount of substance released may be performed manually, such as by a person sensing that a plume can be detected by odor, or the like, or may be made by one or more sensors that are adapted to measure a concentration of the substance. If a sensor is used, the sensor may be a stationary sensor or a portable sensor. If a portable sensor is used, the portable sensor may be a wireless sensor. Furthermore, the portable sensor may be positioned at the beginning of the substance released, such as downwind of the release location. The portable sensors may be moved during the event. If so, attempts to collect data would resume after the move.
A determination may be made that a particular measurement is a valid measurement and projecting that particular measurement back in time in order to obtain a concentration measurement prior to the valid measurement being obtained. The measurement may be projected back in time to when the sensor was first impacted by the plume. Furthermore, measurements from a sensor may be no longer used when the sensor has reached a maximum measurement for the capabilities of the sensor.
A predicted profile of time and concentration measurements may be provided and the concentration measurements compared with the predicted profile. The predicted profile may be revised in response to the outcome of comparing. The algorithm may be performed until convergence with the predicted profile has occurred. Multiple measurements may be made in each of multiple different locations and an estimate of the amount of the substance released may be obtained as a function of the multiple concentration measurements at each of the locations and a time of the measurements.
A substance release rate estimation system for estimating an amount of substance released from a plume created by the release, according to another aspect of the invention, includes at least one sensor, an atmospheric conditions input, and a computer system that is programmed with an algorithm. The at least one sensor is positioned at the plume and measures concentration of the released substance. The atmospheric conditions input is adapted to input atmospheric conditions. The computer system receives concentration measurements from the sensor and atmospheric conditions from the atmospheric conditions input. The algorithm generates an estimate of a substance released from the concentration measurements and the atmospheric conditions.
A substance release estimation system for estimating an amount of released substance whose release creates a plume, according to another aspect of the invention, includes at least one sensor and a computer system programmed with an algorithm. The at least one sensor is adapted to be positioned at a plume and makes multiple concentration measurements of the released substance over time. The computer system receives concentration measurements from the at least one sensor. The algorithm generates an estimate of substance release from multiple ones of the concentration measurements that are obtained from the at least one sensor over time.
These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.